A lead acid battery is being widely used for a power source for starting an automobile engine and a power source for supplying electric power to various electrical equipments. The lead acid battery includes such a problem that a high-rate discharge performance of a negative electrode is deteriorated earlier than that of a positive electrode when charge/discharge operations are repeated, so that a battery life is limited due to the negative electrode. The cause is supposed to be attributable to a fact that a negative active material shrinks due to charge/discharge to cause a decrease in a surface area of the negative active material. In order to dissolve the above problem, a negative active material becomes used which is prepared by adding a lignin having a unit structure represented by the formula (III) to a lead oxide.

In this instance, the lignin is a component included in a wood, and is a by-product produced when manufacturing pulp in a paper making factory. Since there are many processes for manufacturing pulp, it can be said that there are so many kinds of the lignin corresponding to those processes. The lignin of the formula (III) is called lignosulfonate which is produced by a method of sulfite digesting. Since sulfurous acid is used in this method, sulfonic acid group is introduced into α-position of the side chain in the structure. The lignin of the formula (III) has a merit of large water-solubility, but has a demerit that it can not be modified easily.
On the other hand, a Pb—Sb alloy has conventionally been used for a positive electrode grid in the lead acid battery. However, a type of the lead acid battery using the Pb—Sb alloy includes such a problem that antimony in the alloy causes a lowering of a hydrogen over-voltage of the negative electrode, so that its maintenance becomes troublesome because a periodic supplement of water becomes required due to an increase of the electrolyte's decrease. For this reason, a hybrid type lead acid battery using the Pb—Sb alloy which has an antimony content half as much as a conventional battery, has been put in use. However, a calcium type lead acid battery using a Pb—Ca alloy is getting a large share in the market of the lead acid battery.